POACEAE. 21 



1. A. odoratum L. Steins 3-6 dm. tall, erect, tufted: leaf -blades 1-15 cm. 

 long, 2-6 mm. wide : panicle 2-6 cm. long : spikelets 8 mm. long. Common, in 

 fields and pastures. Nat. of Eu. Sum. SWEET VERNAL-GRASS. 



15. ARISTIDA L. Tufted grasses, with narrow and often convolute or 

 setaceous leaf -blades and contracted or open panicles, which are sometimes 

 nearly racemose. Spikelets 1 -flowered, narrow. Scales 3, the outer 2 mem- 

 branous, persistent, empty, narrow, keeled, awnless, usually longer than the 

 third scale which is of firmer texture, narrow, rigid, strongly convolute about 

 the 2-nerved palet and the perfect flower, often with a prominent callus at the 

 base, 3-awned from the apex, the generally spreading awns glabrous to plumose, 

 the central awn commonly flexuous, coiled, or bent, the lateral awns often 

 shorter, occasionally very short and erect, the 3 awns sometimes more or less 

 connate at the base and the column thus produced articulated to the scale. 

 Stamens 3. Styles distinct. Stigmas plumose. POVERTY-GRASS. WIRE-GRASS. 



Central awn coiled at the base. 1. A. dicUotoma. 

 Central awn not coiled at the base. 



First scale shorter than the second. 2. A. gracilis. 



First scale longer than the second. 3. A. purpurascens. 



1. A. dichotoma Michx. Stems 2-6 dm. tall: leaf -blades 2-9 cm. long, 1.5 mm. 

 wide or less: panicle 3.5-7 cm. long, the branches erect: spikelets 7-9 mm. 

 long, the 2 outer scales about equal in length, or the first a little the shorter, 

 usually awn-pointed, the flowering scale 5-7 mm. long, the lateral awns very 

 short, erect, the central awn spreading, the straight portion 2-5 mm. long, rarely 

 longer. Common, in dry soil. Sum. and fall. 



2. A. gracilis Ell. Stems 1.5-6 dm. tall, slender: leaf -blades 3-12 cm. long, 

 1 mm. wide or less : panicle 5-15 cm. long, its short branches appressed : spike- 

 lets 5-7 mm. long, the 2 outer scales usually awn-pointed, the flowering scale 

 56 mm. long, more or less hispidulous, especially on the keel, the central awn 

 spreading, 6-10 mm. long, the lateral awns erect, 1-3 mm. long. N. Bare, 

 in sandy soil. Sandstones and shales. Sum. 



3. A. purpurascens Poir. Stems 3-8> dm. tall: leaf -blades 0.5-2 dm. long, 1-2 

 mm. wide, flat, long-acuminate: panicle 1.5-3 dm, long, its branches appressed: 

 spikelets 9-12 mm. long, the 2 outer scales 1-nerved, the first one usually exceed- 

 ing the second, occasionally equalling it, the flowering scale 68 mm. long, the 

 awns more or less spreading, especially the central one which ia 1.5-2.5 cm. 

 long, the lateral awns from | as long to nearly equalling it. Lower Susque- 

 hanna valley. Bather rare, on the banks of the river. Schists. Sum. and fall. 



16. STIPA L. Tufted grasses, with convolute or flat leaf -blades and 

 terminal contracted or open, often slender, panicles. Spikelets narrow, 1- 

 flowered, usually few and large, or sometimes smaller and numerous. Scales 

 3, the 2 outer empty, persistent, narrow, keeled, acute, rarely awned, the third 

 scale tightly convolute about the 2-nerved or 2-keeled palet and the perfect 

 flower, rigid, narrow, the apex usually attenuated into a more or less geniculate 

 awn (or rarely 2-toothed or shortly 2-cleft, with the awn strict and arising 

 between the teeth) which is often spiral or twisted at the base, and generally 

 deciduous at the articulation to the scale, rarely not articulated and persistent. 

 Stamens 3, or rarely fewer, the anthers very often barbellate at the apex. Styles 

 short, distinct. Stigmas plumose. FEATHER-GRASS. 



1. S. avenacea L. Stems 3-8 dm. tall: leaf -blades involute -filif or m : panicle 

 1-2 dm. long, its branches lax and finally spreading: empty scales of the 



